Re: [tsvwg] I-D Action: draft-ietf-tsvwg-udp-options-dplpmtud-09.txt

[Erik Auerswald <[e-mail]>]

Hi Gorry,

On Sun, Jul 02, 2023 at 07:59:34PM +0100, Gorry Fairhurst wrote:
> On 02/07/2023 19:32, Erik Auerswald wrote:
> >Hi,
> >
> >thanks for the additional text in section 4.4!
> >
> >After re-reading the draft, I have noticed four additional issues resp.
> >potential improvements:
> >
> >
> >(1)
> >
> >In section 4.3 on page 8, section 4.2 of RFC 8899 is given as reference for
> >a DPLPMUTD black-hole.  This should be section 4.3 of RFC 8899 (Black Hole
> >Detection and Reducing the PLPMTU) instead, I'd say.
> >
> >OLD:
> >
> >   (Section 5.2 of [RFC8899], Section 4.2 of [RFC8899]
> >   defines a DPLPMTUD black-hole).
> >
> >NEW:
> >
> >   (Section 5.2 of [RFC8899], Section 4.3 of [RFC8899]
> >   defines a DPLPMTUD black-hole).
> 
> Thanks, done in this PR for the editor's version.
> 
> See:
> 
> https://github.com/uoaerg/draft-udp-options-dplpmtud/pull/28/files#diff-768474f5b48a4bc0b418862bf044141c340e502c6f99947161841e6137601c85

The PR looks mostly good, but the "black-hole" reference is mixed up.

Currently, this draft has two references to "black hole" as described by 
RFC 8899.  One references section 4.2 (wrong), one references section 4.3
(correct).

```
$ grep '4\..\.  Black.Hole' rfc8899.txt 
     4.3.  Black Hole Detection and Reducing the PLPMTU
4.3.  Black Hole Detection and Reducing the PLPMTU
```

The linked pull request changes the correct reference to be incorrect.

> >
> >(2)
> >
> >Then there seems to be an inconsistency in a sentence in section 4.3 on
> >page 9.  There are three alternatives given for a probe packet, but the
> >first ("Probing using padding data") and the third (construct a probe
> >packet that does not carry any application data) seem to be the same.  I'd
> >suggest to just remove the last alternative:
> >
> >OLD:
> >
> >   A probe packet used to validate the path MAY use either
> >   "Probing using padding data" or "Probing using application data and
> >   padding data" (Section 4.1 of [RFC8899]) or can construct a probe
> >   packet that does not carry any application data, as described in a
> >   previous section.
> >
> >NEW:
> >
> >   A probe packet used to validate the path MAY use either
> >   "Probing using padding data" or "Probing using application data and
> >   padding data" (Section 4.1 of [RFC8899]).
> >
> I agree this was unclear, I suggest the revised text in the PR.

Looks good. :-)

> >(3)
> >
> >IMHO the text would be easier to understand if all UDP Options used were
> >introduced together, i.e., in section 3, e.g., as follows:
> >
> >OLD:
> >
> >   In this specification, this is realised using a pair
> >   of UDP Options: the Request (REQ) Option and the Response (RES)
> >   Option [I-D.ietf-tsvwg-udp-options].
> >
> >NEW:
> >
> >   In this specification, this is realised using three
> >   UDP Options: the End of Options List (EOL) Option,
> >   the Request (REQ) Option, and the Response (RES) Option
> >   [I-D.ietf-tsvwg-udp-options].
> >
> Kind of, but I think the focus is on REQ/RES. Maybe though to be
> complete I could suggest:
> 
> The method also uses the the End of Options List (EOL) Option <xref
> target="I-D.ietf-tsvwg-udp-options"></xref>. to
> introduce padding to set the size of a probe packet.</t>

That looks good, too (but there is a stray period after "</xref>" before
"to").

> >(4)
> >
> >Similarly, section 3.1 could also include all the UDP Options features used
> >for DPLPMTUD.  This could be accomplished by extending the first sentence
> >of section 3.1 and adding another bullet point before the first one:
> >
> >OLD:
> >
> >   The UDP Options used in this document are described in Section 9.7 of
> >   [I-D.ietf-tsvwg-udp-options] and are used in the following way:
> >
> >   *  The REQ Option is set by a sending PL to solicit a response from a
> >      remote receiver.  A four-byte token identifies each request.
> >
> >NEW:
> >
> >   The UDP Option features used in this document are described in Section
> >   9.1, Section 9.7, and Section 13 of [I-D.ietf-tsvwg-udp-options] and
> >   are used in the following way:
> 
> I'm inclined to remove the cross reference. References to sections
> are rather fragile
> 
> if specs are updated, and the sections can be found from the ToC, so
> perhaps it
> 
> might be better without, see PR.

That looks good in the PR.

> >   *  A sending PL uses the EOL option together with a minimum datagram
> >      length to pad probe packets.
> 
> I see, I propose;
> 
>                      <t>A sending PL can use the EOL option together
> with a minimum
>                        datagram length to pad probe packets.</t>

That is fine.

> >
> >   *  The REQ Option is set by a sending PL to solicit a response from a
> >      remote receiver.  A four-byte token identifies each request.
> >
> >
> >Regards,
> >Erik
> >
> >
> >On Thu, Jun 29, 2023 at 10:08:16AM -0700, [e-mail] wrote:
> >>A New Internet-Draft is available from the on-line Internet-Drafts
> >>directories. This Internet-Draft is a work item of the Transport Area Working
> >>Group (TSVWG) WG of the IETF.
> >>
> >>    Title           : Datagram PLPMTUD for UDP Options
> >>    Authors         : Godred Fairhurst
> >>                      Tom Jones
> >>    Filename        : draft-ietf-tsvwg-udp-options-dplpmtud-09.txt
> >>    Pages           : 17
> >>    Date            : 2023-06-29
> >>
> >>Abstract:
> >>    This document specifies how a UDP Options sender implements Datagram
> >>    Packetization Layer Path Maximum Transmission Unit Discovery
> >>    (DPLPMTUD) as a robust method for Path Maximum Transmission Unit
> >>    discovery.  This method uses the UDP Options packetization layer.  It
> >>    allows an application to discover the largest size of datagram that
> >>    can be sent across the network path.  It also provides a way to allow
> >>    the application to periodically verify the current maximum packet
> >>    size supported by a path and to update this when required.
> >>
> >>The IETF datatracker status page for this Internet-Draft is:
> >>https://datatracker.ietf.org/doc/draft-ietf-tsvwg-udp-options-dplpmtud/
> >>
> >>There is also an htmlized version available at:
> >>https://datatracker.ietf.org/doc/html/draft-ietf-tsvwg-udp-options-dplpmtud-09
> >>
> >>A diff from the previous version is available at:
> >>https://author-tools.ietf.org/iddiff?url2=draft-ietf-tsvwg-udp-options-dplpmtud-09
> >>
> >>Internet-Drafts are also available by rsync at rsync.ietf.org::internet-drafts
> >>
> >>
> Best wishes,
> 
> Gorry

Regards,
Erik